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News on the TSPAS package by Timo Salmi in reverse order ======================================================== University of Vaasa, Finland, Sun IPX sparcstation garbo.uwasa.fi has a large collection of PD and shareware PC programs available by anonymous ftp and mail server. The file /pc/ts/0news-ts contains news about the TS-programs in the /pc/ts directory (in reverse order). This text, which you now have, is an extract from the 0news-ts file and the UseNet news. .................................................................. Prof. Timo Salmi Moderating at garbo.uwasa.fi anonymous FTP archives 128.214.87.1 Faculty of Accounting & Industrial Management; University of Vaasa Internet: ts@uwasa.fi Bitnet: salmi@finfun ; SF-65101, Finland .................................................................. ┌────────────────────────────────────────────────────────────────┐ │ Appeal: Let me take up a request for those of you who may have │ │ found my programs or units useful. As I am not asking for a │ │ registration fee for the PD versions, would you do me a │ │ reciprocal favor by uploading at least some of my packages to, │ │ say eg one local bulletin board (BBS), and thus contribute to │ │ disseminating the *latest* versions of these packages. And, │ │ if you distribute these packages, would you PLEASE distribute │ │ an entire package, not individual programs from within any │ │ package. This is a request that all of us share who write PD │ │ programs. │ └────────────────────────────────────────────────────────────────┘ Sun 8-Nov-92: I have again updated my Turbo Pascal units collection. It is now garbo.uwasa.fi:/pc/ts/tspa31*.zip where * = 40,50,55,60. The new routines added are TSUNTB: BBINFN Convert decimal byte to binary string BHEXFN Convert decimal byte to hexadecimal string TSUNTE: ARCFILFN Is a file's archive bit set or not HIDFILFN Is a file a hidden file or not RDOFILFN Is a file a read-only file or not SYSFILFN Is a file a system file or not TSUNTG: ACTDRVFN Which floppy drive is active on a one drive system FLOPSTFN Floppy disk status. Is it present and formatted. ISUBSTFN Is a drive a substituted drive (MsDos 3.1+) MEDIAFN What kind of a disk media is present in a drive returns: $00 : Error $F0 : Floppy of 1.44Mb $F8 : Fixed disk $F9 : Floppy of 1.2Mb $FA : Floppy of 720Kb $FD : Floppy of 360Kb $FF : Floppy of 320Kb TSUNTJ ISDIR2FN Is a name a directory or not, alternative method Sun 20-Sep-92: In my Turbo Pascal units there is a number of editable readln substitutes: TSUNTF: (uses Dos, Crt) EDRDLN Readln with line-editing potential (the simplest) EDREABLN Edreadln with ctrl-c and break trapping EDREADLN Editable Readln with recall, and insert toggle I have written alternative versions of these routines which can take a PrefillString as the default input string, so the user has an option of just pressing enter, and default is selected. EDRDEBLN Editable Readln with ctrl-c, break trapping, pre-fill etc EDRDEFLN Editable Readln with recall, pre-fill, and insert toggle The suggestion to make this enhancement came from Darrell Davis davisd@ziavms.enmu.edu. My thanks to Darrell for his useful suggestion. garbo.uwasa.fi:/pc/ts/tspa3040.zip garbo.uwasa.fi:/pc/ts/tspa3050.zip garbo.uwasa.fi:/pc/ts/tspa3055.zip garbo.uwasa.fi:/pc/ts/tspa3060.zip Wed 26-Aug-92: Updated my Turbo Pascal units collection. It is now garbo.uwasa.fi:/pc/ts/tspa29*.zip where * = 40,50,55,60. Bug fixed (hopefully) the ISDIRFN "Is a name a directory or not" function in TSUNTJ unit. My thanks are due to Richard (Ricki) Breuer ricki@rwthi3.informatik.rwth-aachen.de for alerting me to the problem. In the process we noticed a rather undesirable feature of DRDOS. All my units are written for MsDos (command.com). The alternative command interpreters like DRDOS and 4DOS can cause incompatibilities since some of Turbo Pascal's routines (like IOResult) utilize the values the system returns. There is nothing I can do about incompatibilities like this, and it is a coincidence that we even noticed, since I do not run 4DOS or DRDOS. Anyway, ISDIRFN eill not work as expected if you are using DRDOS. I do not know about 4DOS. SETENV "Set a parent environment variable (variable=value)" in the TSUNTENV unit now accepts cases like TARGET=A B C (formerly the it was cut at the spaces). Also this suggestion is to to Ricki. Be careful. Trailing white spaces and other invisible characters you might put in there are included. Thus "TARGET=A" and "TARGET=A " are not the same thing. Started a new 4.0+ specific unit TSUNTK. It contains the following routines. BOOTDRFN Get boot device name (MsDos 4.0+) GETSERFN Get disk's serial number (MsDos 4.0+) GETVOLFN Special get disk volume label (MsDos 4.0+) SETSER Set floppy's serial number (MsDos 4.0+) The first, that is BOOTDRFN was transferred from the TSUNTH unit. The others are brand new. I got the idea to get and set the disk serial number from PC-Magazine (July 1992, Vol. 11, No. 13, p. 496) which published TP 6.0 specific code for these tasks. Since my own TP units are more general, that is for all the current MsDos TP versions starting from TP 4.0, I decided to write routines of my own for these tasks. But the users interested in a source code may wish to look at the article. (I did not bother to test whether the PC-Magazine code works, but I don't see why not). I got interested because I now use MsDos 5.0 in addition to 3.30 and 3.21 (and the aggravating 4.01). Added HEXLNGFN "Convert hexadecimal string to decimal longint up to 7FFFFFFF" to the conversion unit TSUNTB because TSUNTK internally needs this conversion in accessing the disk serial number. Added to TSUNTE the following elementary routines, just because I occasionally happen to need them myself. LABELFN Get a disk's volume label (not for TP 4.0) DEFDRVFN Get the default drive Finally added HIBACK to TSUNTC to enable high intensity background colors instead of enabling blinking text. The appropriate interrupt was pointed out by Robert Beauchaine bobb@vice.ICO.TEK.COM on the UseNet news in comp.lang.pascal. The routine requires an EGA, MCGA, or a VGA. Sat 13-Jun-92: Updated my Turbo Pascal units collection. It is now garbo.uwasa.fi:/pc/ts/tspa28*.zip where * = 40,50,55,60. Added to TSUNTG unit GETESCAN Get scancode of key pressed, enhanced keyboard. GETSCAN Get scancode of key pressed, XT keyboard. The TSUNTENV unit already had SETENV Set a parent environment variable (variable=value). but this takes effect only after the program has been completed. Added an alternative which takes effect immediately, but is temporary SETENVSH Set an environment variable for the duration of shelling. One of the handy uses of SETENVSH is that you can temporarily change the prompt to indicate that you are shelled out of a program so that you are less likely to forget to type exit. See TSUNTG.TST for how to use this feature. Sat 8-Feb-92: I have updated my Turbo Pascal units collection to be garbo.uwasa.fi:/pc/ts/tspa2740.zip garbo.uwasa.fi:/pc/ts/tspa2750.zip garbo.uwasa.fi:/pc/ts/tspa2755.zip garbo.uwasa.fi:/pc/ts/tspa2760.zip This time I have introduced (parent) environment related routines in a new TSUNTENV.TPU unit ENVSIZFN Get the size of the parent environment ENVUSEFN Get the current use of the parent environment ENVADDFN Get the starting segment address of the parent environment SETENV Set a parent environment variable (as MsDos SET var=value) SHOWENV Write the parent environment table on stdout (for testing) Setting a parent environment variable from within a Turbo Pascal program can be considered reasonably advanced programming I guess, and I cannot be absolutely sure that I got it right. But here goes anyway. The key to the task is obtaining the starting address of the parent environment, and knowing that the format of the parent environment table in memory is name=value1<nul>name=value2<nul>...name=valueN<nul><nul>. PC Magazine Vol. 11, No. 1, pp. 425-427 has useful code which can be adapted to find out the relevant segment address. Should you look at that article, the crucial variable to get at in there is EnvSeg. The rest then follows. What a delightfully complicated challenge. Oh yes, since I know that some users will be asking for the source code. I am happy to share this reference, and make my .TPU collection publicly available, but I have chosen not to distribute by source codes. In fact I have not added the unit to the tspas2740.zip TP 4.0 version TPUs, but I have updated it nevertheless to avoid confusion with the version numbers. Mon 6-Jan-92: I have updated my Turbo Pascal units collection to be garbo.uwasa.fi:/pc/ts/tspa2640.zip garbo.uwasa.fi:/pc/ts/tspa2650.zip garbo.uwasa.fi:/pc/ts/tspa2655.zip garbo.uwasa.fi:/pc/ts/tspa2660.zip by transferring the following routines from TSUNTH.TPU unit to a new TSUNTJ.TPU unit COPYFILE Copy a file from within a Turbo Pascal program OPENEDFN Is an assigned textfile still open or not ISDIRFN Is a name a directory or not PIPEDIFN Is the standard input from redirection PIPEDNFN Is the standard output redirected to nul PIPEDOFN Is the standard output redirected by adding the following routines to TSUNTJ.TPU INTRADDR Show the memory address to which the interrupt points INTRLOCA Show the memory address where the interrupt is located and by adding the following routines to TSUNTH.TPU ISMOUSFN A simple true/true false test of mouse available MOUSTAFN Status (type byte) of the mouse hardware and driver My thanks are due to Duncan Murdoch in particular who first noted a potential error in the early version of my mouse functions. The first of the sets garbo.uwasa.fi:/pc/ts/tspa2640.zip contains a compatibility unit TSUNT45.TPU for Turbo Pascal 4.0. It adds routines that the later versions have, but which are missing in version 4.0. I have added GetVerify Get the status of the MsDos write verify flag SetVerify Set the status of the MsDos write verify flag GetCBreak Get the state of Ctr-Break checking in DOS SetCBreak Set the state of Ctr-Break checking in DOS Sun 27-Oct-91: I have updated my Turbo Pascal units collection to be garbo.uwasa.fi:/pc/ts/tspa2540.arc garbo.uwasa.fi:/pc/ts/tspa2550.arc garbo.uwasa.fi:/pc/ts/tspa2555.arc garbo.uwasa.fi:/pc/ts/tspa2560.arc by adding the following routines ISANSIFN Has ansi.sys a a similar driver been loaded BTEWRDFN Combine two bytes into a single word, inverse of Hi & Lo WRDLNGFN Combine two words into a longint HIWORDFN The high-order (hi) word of the longint argument LOWORDFN The low-order (lo) word of the longint argument Sun 21-Jul-91: I have updated my Turbo Pascal units collection to be /pc/ts/tspa24##.arc (where ## = 40, 50, 55, and 60). Turbo Pascal 5.0 (and later) introduced some routines which are not present in version 4.0. My Turbo Pascal units collection (the 4.0 version) includes a TSTPU45 unit which introduces some of the missing routines also to TP 4.0. I have added FExpand (Expand a file name into a fully qualified file name) to this unit. Occasionally you will want to be able to tell where the standard input to your program comes from. Does it come in the normal way from the keyboard, or does it come from redirection. Likewise, you may wish your program to know whether its standard output goes to the screen, or is it redirected to a file or through a pipe. The new boolean functions in the TSUNTH.TPU unit will give this information: PIPEDIFN Is the standard input from redirection PIPEDOFN Is the standard output redirected PIPEDNFN Is the standard output redirected to nul Other new routines in the TSUNTH unit include: BOOTDRFN Get boot device name (MsDos 4.0+) DATEFMFN Country-dependent date format (MsDos 3.0+) NRCYLFN Number of cylinders on a drive if media present (MsDos 3.2+) TIMEFMFN Country-dependent time format (MsDos 3.0+) Z2ASZFN Convert an Asciiz string into an ordinary ascii string Tue 8-Jan-91: My Turbo Pascal units collection is now available also for Turbo Pascal 6.0. It is /pc/ts/tspa2360.arc, and is in no other way different from tspa2340.arc, tspa2350.arc, and tspa2355.arc except that the units are for 6.0. As you know, Turbo Pascal units are not compatible across versions. Sat 5-Jan-91: I have upgraded my Turbo Pascal units collection at uwasa.fi archives by making several changes. Most importantly I have divided the package into three parallel packages: tspa2340.arc for Turbo Pascal 4.0 version tspa2350.arc for Turbo Pascal 5.0 version tspa2355.arc for Turbo Pascal 5.5 version Thus you'll only need the package concurring with the Turbo Pascal version you use yourself. With the exception of the differences inherent to the different releases of Turbo Pascal, the packages are the same. I am expecting Turbo Pascal 6.0, but it has not arrived yet. I have added a new unit TSERR.TPU which turn on the verbal run-time error messages. It is very easy to use. Just include uses TSERR; at the beginning of your main program and you'll have verbal run-time error messages besides the original, cryptic error codes. I have done some cleaning of the old units by omitting some of the older routines which have a more efficient later replacement. In particular this concerns the functions for converting values from one base to another. There are also new routines: PARSENFN Number of substrings in a string (resembles ParamCount) PARSERFN Get substrings from a string (resembles ParamStr) FATSFN Get number of file allocation tables, not XTs INTERLFN Get interleave coefficient of a harddisk, not XTs LASTDRFN Get last drive of the system, softcoded, not XTs and the generic power function POWERGFN has been rewritten. Wed 8-Aug-90: I have updated my Turbo Pascal (4.0, 5.0, 5.5) units collection to be version (/pc/ts/)tspas22.arc. There are several functions which Tubro Pascal 5.0 and 5.5 have, but TP 4.0 does not. I have added a new unit tsunt45.tpu which includes some of these functions such as EnvCount, EnvStr, GetEnv, and ParamStr0 (giving the name of the program). The unit tsunti.tpu can be used to put information into the .exe file and perform selftests of the .exe. This unit is now also available for TP 4.0. Turbo Pascal ReadKey lacks the ability to read special keys such as RightShift, LeftShift, RightCtrl, and so on. Functions to detect pressing these keys have been added. Turbo Pascal ReadKey also lacks the ability to cope with the full enhanced keyboard potential. This means that TP ReadKey does not detect pressing F11 or F12, and that it cannot distinguish between the numeric keyboard cursor keys and the grey cursor keys. I have added a RDENKEFN function which has these abilities. Wed 1-Aug-90: I have updated my Turbo Pascal (4.0, 5.0, 5.5) units collection to be version (/pc/ts/)tspas21.arc. Turbo Pascal version 4.0 does not have the DosVersion function available in versions 5.0 and 5.5. I have written this function for version 4.0. Furthermore the lack of this function caused errors in TP 4.0 versions of my last two units. This has been put right. I have included a new unit (tsunti.tpu) for putting information into the .exe file, and retrieving the information (not for TP 4.0). The routines include a method for calculating the direct checksum for a file (eg for virus checking). This is not as trivial as it may sound at first sight, because in calculating the checksum, the checksum constant within the program must be skipped. (Else a change in the checksum constant would alter the checksum resulting in a "vicous circle"). Also, the method must be fast enough. I have also included a fast a date and filesize checking method for detecting if the .exe has been pacthed or its size altered. (Of course, the checksum method is much more difficult to defeat, but it is more complicated and not as fast). Here I have made an exception and included the source code. It is in the selftest.pas file within tspas21.arc. Mon 23-Jul-90: I have updated my Turbo Pascal (4.0, 5.0, 5.5) units collection to be version (/pc/ts/)tspas20.arc. One problem area that has intrigued me for some time is finding a technique for storing information within an executable file and updating that information. I've looked into it and written a couple of relevant procedures. USECOUNT keeps track of how many times the program has been run and stores the result within the .exe file. BRANDEXE is a more general, but also a more complicated procedure for .exe file handling. As an example I have a demonstration how to tell the previous time when the program was run. The function checking the on-line status of the printer (prnonlfn) has been rewritten to work without Turbo Pascal's Crt unit. And an alternative printer on-line status function, LTPONLFN, has been added. This one should be more robust, because it actually tries to send a carriage return to the printer, and observes the resultant success of the operation to define the on-line status. Of course this is achieved by {$I-} {$I+} IOResult testing, but the real trick here is make to system respond immediately rather than in the default response time of up to one minute. A new procedure PRTSCR sends the current screen to the printer. The new routines GETPRTFN and SETPRT get and set respectively the number of printer default retry times before a timeout. TICKSFN is a simple complement to the TIMERFN already in the collection. TICKSFN gives the number of clock ticks (there are 18.2 per second) since midnight. A new LASTDMFN returns the number of days in a given month and year. DATEOKFN tells whether a date is a valid, existing date. ZELLERFN lets you compare which of the two dates is earlier, calculate the number of days between two dates etc. A new FIXEDFN returns whether a drive is a fixed disk or not. MATHCOFN returns if a math coprocessor is present. RS232FN returns the number of serial ports. PARPORFN returns the number of parallel ports. COUNTRFN returns the country code. CHIPFN returns the type of the processor chip. There are new keyboard routines. SCRLONFN gets the current ScrollLock status. CAPS, NUMLOCK, and SCRLOCK respectively set the CapsLock, NumLock and ScrollLock on, or off. They take the desired status as a boolean argument. CLS sets 25*80 text mode and clears the screen and CLS40 does likewise for 25*40. Crt is not required. So far none of the routines in the TSPAS collection have included any inline code. Starting from tspas20.arc this no longer holds. I have tried to understand some assembler and have included also inline code. Be warned that I cannot give any guarantees that the inline coded routines won't cause confusion. Where inline code has been used, I have stated so. The first function to utilize this is LOWCASFN which is the exact opposite of Turbo Pascal's own UpCase function. WARMBOOT simulating alt-clr-del, and COLDBOOT reboot with memory tests are new, inline routines. A couple of routines have been moved from one unit to another. Newsgroups: comp.lang.pascal From: ts@chyde.uwasa.fi (Timo Salmi) Subject: Redirecting writes to the printer Organization: University of Vaasa Date: Sun, 22 Jul 90 03:58:00 GMT (* About half a year ago several posters wanted to find a way to direct all output to the printer. (To enable a documentation of students' programming tasks.) For some reason nobody of us then found a simple working solution, which is outrageously elementary, after fact. There are, of course, alternative solutions, the most complicated being writing a new device driver. An intermediate (easier) solution is to juggle with certain TP predefined constants. I have two procedures USECON and USEPRN (in /pc/ts/tspas19.arc tpu collection) which when placed anywhere within the program will change the output device. But below is an example the the easiest alternative needing no accessories. *) program HowToRedirectAllOutputEasilyToThePrinter; {$DEFINE printit} begin {$IFDEF printit} assign (output, 'prn'); rewrite (output); {$ENDIF} : writeln ('From Timo Salmi: Hello world, and whatever else'); : {$IFDEF printit} close (output); {$ENDIF} end. (* thus endeth the escapade *) Thu 14-Jun-90: I have updated my Turbo Pascal (4.0, 5.0, 5.5) units collection to be version (/pc/ts/)tspas19.arc. The function INDRIVFN in tsuntg.tpu tests whether a device is present in a drive. If you defined an invalid drive (such as '1'), a run time error occurred in my earlier versions. - Tsunta.tpu has a new function HIGHTFN, which gives the height of the screen by resolution (25, 43 or 50). - Tsuntf.tpu has a third enhanced readln with line editing, recall, insert toggle, and clean break potential. - Tsunth.tpu includes a new function ISDIRFNto test whether a name is a directory. - COPYFILE procedure copies a file from within a Turbo Pascal program and returns a success status code. I have seen postings in the (InterNet) news about problems with copying files in Turbo Pascal, but I hope that this one should do the trick. - OPENEDFN function indicates whether a text file has already been closed within the program, or if it is still open. This is particularly convenient for procedures aborting your program. - Tsuntd includes a new procedure called AUDIO. It is an enhanced version of Turbo Pascal's own sound procedure. It takes frequency and duration as parameters, and it does not need the presence of the interfering Crt unit. Audio was written in collaboration with Ari Hovila (ajh@chyde.uwasa.fi). - And since I am often asked the question, sorry, no, dear fellow users, the sources are not available, only the units and their documented interfaces. Sun 25-Feb-90: I have gotten repeated requests from the users for a Turbo Pascal 5.5 version of my Turbo Pascal units collection. I now have finally got the 5.5 compiler, courtesy of University of Vaasa, because it was felt here that this international interaction is important enough to warrant the expense. (As I have told many of the users who have contacted me in this matter, I am not yet interested in OOP myself). Hence I am in a position to oblige. The new version is called tspas18.arc. There is only one new function in the collection this time. The main point was providing the TP 5.5 versions of the units. Thus there are now three versions of each unit in this new release: TP 4.0, 5.5, and 5.5. - It is true that Borland has made excellent products for the PC community, but the incompatibility between the TPUs of the different Turbo Pascal versions has many of us users disgruntled. Wed 6-Dec-89: Updated the Turbo Pascal 5.0 (and 4.0) units collection to be version /pc/ts/tspas17. The new procedures include WHEREXFN and WHEREYFN which locate the cursor position without the Crt unit. As you will recall Crt unit includes a WhereX and a WhereY function. The reason I have prepared alternatives to Crt functions and procedures in this, and the earlier releases, is because with some incompatible PCs the Crt unit causes problems, and redirection requires special measures with the Crt. - KEYPREFN is a replacement of KeyPressed and READKEFN for ReadKey. - CLUSIZFN gives the cluster size on a device. ALLSIZFN gives the true total size allocated to a file instead of the size shown on ordinary directory listings. - INKEYFN is a Basic-like timed input. Tue 28-Nov-89: Some time ago there was a lively discussion in the InterNet news group comp.lang.pascal how to redirect all write and writeln statements to the printer without having to change the statements. I now have a solution to that problem for Turbo Pascal 4.0 and 5.0. The procedures USEPRN and USECON are part of update /pc/ts/tspas16.arc of my Turbo Pascal 5.0 and 4.0 units collection. The new procedures/functions also include WEEKNRFN function in the TSUNTE unit. It gives the weeknumber for a given date. REVCOLOR in TSUNTC reverses (toggles) text colors. And there are many other new routines making up a new unit TSUNTG. Thu 26-Oct-89: I have a private mailing list for emailing these update news. Especially, if you have my programs downloadable at your site or your BBS you are welcome to ask for inclusion on this list. Wed 18-Oct-89: Released update /pc/ts/tspas15.arc of my Turbo Pascal 5.0 and 4.0 units collection. New procedures/functions include BINFN in TSUNTB for fast conversion of decimal words to binary and HEXFN for fast conversion to hexadecimal. LBIN and LHEX convert long integers fast to binary and hexadecimal respectively. POWERLFN raises a longint to a power, fast. BORDER in TSUNTE changes the border color for CGA or VGA. All the rest of the procedures and functions remain unchanged. Tue 26-Sep-89: Released update /pc/ts/tspas14.arc of the Turbo Pascal 5.0 and 4.0 units collection. The package contains units from tsunta.tpu to tsuntf.tpu. Tsunte.tpu contains a new function cmdlnfn, which gives the entire command line in a program call. The input line-editing procedure edreadln in tsuntf.tpu now has a recall option (CursorUp) and the insert key toggle. I have preserved an edrdln procedure for line-editing without recall and insert. Tsuntd has new ParamCount and ParamStr like functions for obtaining substrings from a string. Sat 19-Aug-89: Released update /pc/ts/tspas13.arc of my Turbo Pascal units. I have rewritten the cursor-size routines in a more general fashion and rearranged the units. One of the weaknesses of the readln statement in (Turbo) Pascal is that it does not allow editing the input-string while giving the input from the keyboard. I decided to do something about this, and wrote an edreadln procedure, which allows to use of LeftCursor, RightCursor, BackSpace, Del, Home, End, and Esc. Of course such routines are very common in input from popup windows. Edreadln is, however, more of a readln-type procedure with normal scrolling capabilities, than a fixed position window routine. This routine is included in the new release. Wed 2-Aug-89: I have released un updated version of the Turbo Pascal units collection tspas12.arc. There are new string routines and detection of the monitor (mono/color) type. ======================================================================= Messages from UseNet news ======================================================================= From ts Sat Jul 28 09:25:43 1990 Subject: Re: Program selftesting and viruses To: 16012_3045@uwovax.uwo.ca (Paul Gomme) Date: Sat, 28 Jul 90 9:25:43 EET DST In-Reply-To: <0649102756@uwovax.uwo.ca>; from "Paul Gomme" at Jul 27, 90 6:19 pm X-Mailer: ELM [version 2.2 PL16] Status: OR > > Programmers: Help fighting viruses and patching. > > > >Viruses and unauthorized patching are problems which should be > >fought against by the PC community. This program demonstrates a > >simple and a reasonably general, fast selftest to detect whether the > >program has caught a virus, or if it has been amateurishly patched. > >The code is easily incorporated in any Turbo Pascal source code. The > >idea is to check whether the file date and size have been altered. > >Most .exe viruses work by appending their code to the .exe file > >altering the file size. Trivial patching changes the file date. > >Either of these is detected by selftest. > > While the idea may have some merits, the execution is flawed. ^^^^^^ No Paul, not flawed. Rather not foolproof, nor is meant to be. > First, it is a minor matter to obtain the creation date of a file. > Consequently, it is a relatively simple matter to apply a patch > which doesn't alter the file size, and restore the original creation > date. Your technique is subject to such an "attack". Certainly. The whole philosophy behind is to have a simple method which staves off any crude attempts. The problem with the more elaborate selfchecks (such as embedded checksums) is that they are difficult to implement. > Second, there are often good reasons to patch a file. Some of these > reasons are cosmetic in nature. Some programs even encourage user > patching. Also true, and then such patching should take care of the date. Or the selftest should have a relevant modification or omission of the date test. > From a more philosophical point of view, I wonder if protection > schemes don't in part encourage those who write viruses. Surely > part of the "thrill" is to avoid detection. Maybe. It can be looked at as a kind of a game. Nevertheless, consider the popularity eg McAfee's virus control programs have gained. Throwing one's hands up in the air is not a good solution. All the best, Timo ======================================================================= From ts Tue Jul 31 12:07:13 1990 Return-Path: <ts> Received: by uwasa.fi (4.1/(hh)29May89) id AA08907; Tue, 31 Jul 90 12:07:12 +0300 From: Timo Salmi LASK <ts> Message-Id: <9007310907.AA08907@uwasa.fi> Subject: selftest To: ts (Timo Salmi LASK) Date: Tue, 31 Jul 90 12:07:11 EET DST X-Mailer: ELM [version 2.2 PL16] Status: O Newsgroups: comp.lang.pascal Path: uwasa.fi!ts From: ts@uwasa.fi (Timo Salmi LASK) Subject: Re: Program selftesting and viruses Message-ID: <1990Jul31.085732.8728@uwasa.fi> Organization: University of Vaasa References: <1990Jul27.182520.12051@uwasa.fi> <1875@krafla.rhi.hi.is> Date: Tue, 31 Jul 90 08:57:32 GMT In article <1875@krafla.rhi.hi.is> frisk@rhi.hi.is (Fridrik Skulason) writes: >This program works in most cases - however, it is not effective against some >of the latest viruses, which fool it by making the program appear unchanged, >after the virus is in control. This is certainly true, and the purpose of the code is to easily weed out elementary cases, which are the most frequent anyway. One of the points was to make the code simple to understand and include. The other alternative is to imbed a checksum in the .exe file. But the code is much more complicated, because the checksum (either direct or crc) constant itself within the program must be skipped when recalculating the checksum. Another problem is that the checksum must be calculated fast. Else it renders the host program useless. I have the code also for calculating and checking the direct checksum of an .exe file in addition to size & date check. This should be fairly effective. This will be included in the upcoming update of my Turbo Pascal units tspas21.arc.